Circuit breaker



E. G. KEES CIRCUIT BREAKER April 7, 1936.

Filed March 15, 1954 INVENTCR Ernesfi hees ATTORN Y WITNESSES Qru. (1%

Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE CIRCUIT BREAKER Pennsylvania Application March 15,

17 Claims.

This invention relates to circuit interrupters and more particularly to an arc extinguisher of the type in which the arc is split up into a plurality of short arcs between conducting plates and then rotated by a radial magnetic field about an annular path until the arc is extinguished.

In arc extinguishers of this type, as disclosed in Slepian Patent No. 1,784,760, issued December 9, 1930, it is desirable to provide a static condenser shield. When the arc has been split up into short arcs between conducting plates, the difierence in potential between each of the plates .is determined by the voltage drop in the short are in each space between the plates. Since the arc extinguisher is usually mounted adjacent to other apparatus or enclosed in a metal clad structure, there is a leakage current from each of the conducting plates to the adjacent grounded metal parts, due to the fact that there is considerable capacitance between each plate and the adjacent metal. This means that the amount of current flowing through the arc across the stack of conducting plates decreases along the stack of plates. The impedance between adjacent plates is substantially constant along the whole stack. The impedance drop which is equal to the product of the current and the impedance, therefore, decreases along the stack of plates. This means that the line voltage across the breaker is not {equally divided between the gaps between the plates but is concentrated at one end of the stack.

In order to control and more nearly equalize the distribution of potential along the stack of plates, a static condenser shield has been positioned along the stack. This condenser shield has comprised a plurality of layers of conduct- .ing material, such as tin foil, imbedded in a laminated member of insulating material. The ends of the static shield have been connected to the arc terminal members of the arc extinguisher. These are terminal members have been connected to the terminals of the circuit connected to the circuit breaker, so that the static condenser shield was connected at all times across the line even when the contacts of the circuit breaker were open. This permitted a small leakage current to flow at all times due to the current conducted through the condenser shield.

An object of this invention is to provide an arc extinguisher of the spaced-plate type in which a condenser shield is provided which is connected so as to be electrically connected in 5 the circuit only while the arc is playing. This 1934, Serial No. 715,617

is accomplished by having at least one terminal of the static condenser shield connected to one of the conducting plates which is spaced, and electrically insulated, from the arc terminal members connected to the circuit terminals. This means that the static condenser shield is connected in parallel with only a portion of the arc and is in series with the remaining portion of the are. As soon as the arc is extinguished, the static condenser shield is therefore, disconnected from the circuit.

Other objects and advantages of this invention will appear from the further description of a specific modification of this invention.

In the drawing:

Figure l is a view partially in section and partially in elevation of an arc extinguisher embodying the invention. The parts in section are shown as a section along the line II of Fig. 2; and

Fig. 2 is a sectional view through the are extinguisher of Fig. 1 taken on the line 11-11.

The are is drawn between a pair of arcing contacts 5 and 'l, which may be operated by any suitable type of mechanism which may also ac tuate main contacts which open prior to the opening of the arcing contacts. The arc drawn by the contacts 5 and l is transferred to a pair of arc horns 9 and II which are provided With upstanding arc-terminal portions [3 and 15. The are extinguishing structure is assembled on a through bolt I! which extends through holes in the arc-terminal members I3 and I5. The bolt H is positioned within an insulating tube IS.

The are extinguisher is made up of a plurality of plate groups 2|, which are alternated along the stack with coil groups 23. Each plate group 2| comprises a plurality of plates 25 of good conducting material such as copper. Each plate 25 comprises an annular portion 2'! and a radially extending portion 29. A V-shaped notch 3| is provided in the extension 29 of each of the plates 25. The conducting plates 25 are spaced and insulated from each other by members 33 which may be of paper having good insulating properties, such as fish paper. The insulating members 33 are shaped so as to form a narrow band which conforms to the shape of the outer edge of the conducting plates 25, with portions extending along the side edges of the extensions 29. The insulating members 33 do not extend to the edges of the the V-shaped notch but provide a path along which the arc may be moved into the annular path 21 of the conducting plates 25. The conducting plates 25 are also spaced apart by a plurality of annular Washers also of insulating paper. The space between the inner edge of the insulating members and the outer edges of the insulating washers 35 provides an annular space between the conducting members in which the arc may be rotated.

Each of the coil groups comprises a spiral coil 31 having a strip of insulating material 39 Wound between the turns of the spiral to insulate them from each other. On each side of the coil is an insulating plate II to provide insulation between the coil and the adjacent conducting plates. On either side of each of the coils is a coil-end plate 43 which is similar in shape to the conducting plates 25, except that they have no extension but are cut off along the edge 45. The inner and outer ends of the spiral coil 31 are each electrically connected to one of the coil-end plates by being soldered thereto. The coils are thus electrically connected in series with the sections of the are playing in the plate groups 2I. The lower portion of each of the coil groups 23 is formed by a plurality of short conducting plates 41 of similar shape to the extensions 29 of plates 25. Each of the short plates 41 has a V-shaped notch therein of similar shape to the notches 3i in the conducting plates 25. The short plates 41 are insulated from each other by insulating members 49 which extend along the top and side edges of the short plates 41.

A static condenser shield 5| is positioned so as to surround the stack of plates. This condenser shield comprises a plurality of layers of tin foil imbedded between layers of insulating material. The insulating material may be paper impregnated with a phenolic condensation resin. After the layers of paper and tin foil have been assembled and impregnated, they are subjected to heat and pressure to form a laminated material of high dielectric strength. As shown in the rawing, there may be provided three layers of tin foil 53, and 51. The tin foil sheets 53 and 51 extend along each end of the shield while the layer 55 is positioned around the central portion of the shield. While the static shield has been shown as being formed with this particular arrangement of layers of tin foil, it is understood that other arrangements may be used without departing from this invention. An alternate form of static shield is shown in Slepian Patent No. 1,910,068, issued May 23, 1933. The layer of tin foil 5'! of the static shield is shown as being connected at 59 to the arc terminal member I5. The other end layer 53 of the tin foil is not con nected to the other are terminal member I3 but is connected at GI to the first plate group 2| at its end spaced from the arc terminal member I3. While the end 59 of the condenser shield has been shown connected to the arc terminal member I5, it may also be connected to one of the conducting plates spaced from the arc terminal member in the same manner as the other end of the static shield.

The arc-drawing contact 5 is connected to one circuit terminal 63 and the other arc-drawing contact 'I is connected to the other circuit terminal 65. When the contacts 5 and I are closed, the circuit is completed directly between the terminals 53 and 55. One end of the conducting bolt I1 is connected through a conductor 61 to the circuit terminal 53 and the other end of the bolt ii is connected by means of a conductor 59 to the arc-terminal member I3. The other arc-terminal member I5 is connected to the circuit terminal 65 and the moving contact I by means of a conductor 'II.

When an arc is drawn between the contact members 5 and I, it is transferred from the contact 5 to the arc horn 9 which is insulated from the contact 5 due to the attraction of an end portion I!) of magnetic material on the arc horn. The short arc portion l3 is immediately extinguished due to the fact that it is paralleled by a lower impedance conducting circuit comprising conductor Bl through bolt I1 and conductor 69. As the moving contact A moves past the other arc horn I I, the other end or" the arc is transferred to the arc horn I I, since the arc horn I I is electrical-.

ly connected to be at the same potential as the moving contact I. The flow of current through the circuit interrupter during half of the alternating current cycle will be from the circuit terminal 63 through conductor 61 through bolt I1, and conductor 69 to the arc horn 9. The current then flows through the arc to the arc horn I I and from the arc horn II to the other circuit terminal 55. It should be noted that the direction of current flow through the arc between the arc horns 9 and II and through the bolt I1 is the same so that the arc is attracted toward the through bolt I1 and is moved into the V-shaped notches 3| due to the magnetic force acting thereon. When the arc reaches the end of the notches, it is split up into short arcs playing in the gaps between the conducting plates. As the ends of the short arcs are moved on to the coil end plates 43, the coils 3! are connected electrically in series with the arc sections playing in each of the plate groups.

Each of the coils 31 sets up a radial magnetic field between the plates 25 of the plate groups 2I. This magnetic field is at right angles to the direction of current flow through the short arcs and rotates them tangentialy to the flux lines around the annular paths 2'! of the conducting plates 25 at a high rate of speed until extinguished.

The distribution of potential between the plates 25 is controlled by the static shield 5I so as to give a substantially uniform potential difference between each pair of plates. By having at least one end of the static shield 5| connected as at 6| to one of the plates which is spaced and insulated from the arc terminal members, the static shield is not conductively connected in the circuit until after the arc has drawn and bridges across the gaps between the plate to which the terminal BI is connected and the arc terminal member. It is thus possible to use one section of the are as a series conductor for connecting the static shield in the circuit. This means that the arc acts as a switching device for connecting the static shield in the circuit when the arc is drawn and for disconnecting the static shield from the circuit as soon as the arc is extinguished. This gives the desirable advantage of not having the static shield electrically connected across the circuit breaker contacts when they are open, and prevents any appreciable leakage current flowing in the circuit due to the capacitance current through the condenser plates of the static shield. While it is still possible that some small current may flow due to the capacitance current across the plate group 2| between the terminal I3 and the plate to which the end SI of the static shield is connected, that current is negligible due to the low capacitance of the group of plates.

Another desirable advantage is obtained due to the fact that the insulating material between the layers of tin foil of the static shield does not have the whole phase voltage of the circuit impressed across it while the breaker is in the open position, as would be the case if the ends of the static shield were connected to the circuit terminals at all times. This relieves the dielectric between the conducting plates of the static shield from dielectric stress except while the arc is play ing so that the dielectric is not solikely to fail due to being continually subjected to high dielectric stress.

While I have described a sp cific embodiment of my invention, it is understood that various changes and modifications may be made without departing from the spirit thereoi.

I claim as my invention:

1. In a circuit interrupter, means for causing an arc, means for equalizing the distribution of potential along said arc, and means of conduct ing material for connecting said equalizing means to a conducting element electrically in the circuit during the existence of said arc only.

2. In a circuit interrupter normally completing an electrical circuit, means for opening the circuit and causing an arc, means for equalizing the distribution of potential along said are, and means for connecting said equalizing means in parallel with a portion only of said arc.

3. In a circuit interrupter, a pair of arc terminal members each connected to one line terminal of the circuit interrupter, means for equalizing the distribution of potential between said are terminal members, and means of conducting material for connecting one end of said equalizing means to a conducting element which is in the circuit upon the playing of an are between said are terminal members and which is out of the circuit immediately upon the extinction of said arc.

4:. In an arc extinguishing device having one end electrically at line potential, a plurality of conducting members positioned across the arc path of said are extinguishing device, and means for equalizing the distribution of potential along said arc path, said equalizing means being connected across a portion of said plurality of conducting members spaced and insulated from said end of the arc extinguishing device electrically at line potential.

5. In a circuit interrupter having one terminal electrically at line potential, an arc extinguishing device, means for establishing a long are, said are extinguishing device including a plurality of conducting members for splitting up said long arc into shorter arcs, means for controlling the distribution of potential between said plurality of conducting members, said controlling means being electrically connected across a major part, but not all, of said conducting members and said major part of the conducting members across which said controlling means is connected being spaced and insulated from said terminal electrically at line potential.

6. In an arc extinguishing device, a plurality of conducting members positioned across the arc path, and means for controlling the distribution of potential along said arc path, said controlling means being connected at each end by means of conducting material in parallel with a portion of said are and in series with another portion of said are whereb said controlling means is deenergized upon the extinction of the second said portion of the arc.

'7. In a circuit interrupter, a pair of arc terminal members electrically connected to the terminals of the circuit, a plurality of conducting members positioned between said are terminal members, a condenser shield having one terminal thereof connected by means of conducting material to one of said conducting members positioned at a point adjacent to but spaced from said are terminal members.

8. In a circuit interrupter having one terminal electrically at line potential, means for causing an are, a condenser shield for controlling the distribution of potential along the arc path, said condenser shield being connected in series with a portion of said are one end of which is at the potential of said terminal electrically at line potential whereby said condenser shield is disconnected from the circuit upon the extinction of said portion of the arc.

9. In a circuit interrupter, means for causing a number of short .arcs to play in series, means for controlling the division of potential between said short arcs, and means using one or more of said short arcs as a series connection to a conducting element conductively connected to said controlling means to connect said controlling means in the circuit and to disconnect said controlling means from the circuit upon the extinction of said one or more short arcs.

10. In a circuit interrupter, a plurality of conducting members, means for causing a plurality of series related arcs to play between a plurality of gaps between said conducting members, means for determining the division of potential between said plurality of gaps, and means of conducting material for connecting said means for determining the division of potential at each end across a plurality, but not all, of said gaps.

11. In a circuit interrupter normally completing an electrical circuit, a plurality of conducting members, means for opening said electrical circuit and causing a plurality of series related arcs to play between a plurality of gaps between said conducting m mbers, and a condenser device having certain plates thereof electrically connected in parallel with one or more of said gaps and in series with one or more of said gaps.

12. In a circuit interrupter normally completing an electrical circuit, a plurality of conducting members each having an annular arc path, means for opening the circuit and causing a plurality of short arcs to play between said conducting member, means for rotating said short arcs about said annular paths, means for controlling the division or"; potential between said short arcs, and means using one or more of said short arcs as a series connection to connect said controlling m ans in the circuit and to disconnect said controlling means from the circuit upon the extinction of said one or more short arcs.

13. In a circuit interrupter normally completing an electrical circuit, a plurality of conducting members, means for opening the circuit and causing a plurality of series related arcs to play between a plurality of gaps between said conducting members, means for causing a magnetic field to rotate said plurality of arcs in the gaps between said conducting members, means for determining the division of potential between said plurality of gaps, and means for connecting said means for determining the division of potential across a plurality, but not all, of said gaps.

14. In a circuit inerrupter, a pair of arc terminal members electri ally connected to the terminals of the circuit, a plurality of conducting members positioned between said are terminal members and insulated from each other, each of said conducting members providing an annular path for the arc, means for causing a magnetic field in the spaces between said conducting members for rotating the arc therebetween, means for controlling the division of potential between said conducting members including a plurality of conducting elements, at least two of said conducting elements being directly electrically connected to the circuit interrupter, and at least one of said connections being to one of said conducting members insulated from said are terminal members.

15. In a circuit interrupter, means for causing an arc, a plurality of conducting plates for splitting said are up into short arcs, means for causing a magnetic field between said plates for rotating said short arcs therebetween, means for controlling the distribution of potential along said conducting plates, said controlling means being electrically connected by means of conducting material at each end across a major part, but not all, of said conducting members.

16. In a circuit interrupter, means for causing an arc, a plurality of conducting plates for splitting said arc up into short arcs, means for causing a magnetic field between said plates for rotating said short arcs therebetween, means for controlling the distribution of potential along said conducting plates, said controlling means comprising a condenser device having one end thereof conductively connected to one of said conducting plates intermediate the ends of said plurality of conducting plates.

17 In a circuit interrupter, means for establishing a long are, a plurality of plates of conducting material between which said arc is split up into a plurality of short arcs, means for equalizing the division of potential between said short arcs, said means being connected across some of said plates of conducting material and in series with the short arcs between other of said plates of conducting material.

ERNEST G. KEES. 

